1. Field of the Invention
The present invention relates generally to wireless transmitters and more particularly to wireless doorbell systems which employ radio frequency (“RF”) transmitters and receivers.
2. Description of the Related Art
Wireless doorbell systems have become an increasingly popular option for persons wishing either to replace their current doorbell system or to add additional doorbells at their place of business or residence. A typical wireless doorbell system generally comprises at least one RF transmitter powered by a battery or other power source, such as existing electrical wiring, and a RF receiver. In response to the depression of a button or other activating means on the transmitter, an electrical circuit is completed within the transmitter which energizes an oscillator or other means for generating a RF signal. The generated RF signal is then, with the aid of an antenna, transmitted a certain distance for reception by the receiver. The receiver alerts, for example, a homeowner that the doorbell button has been depressed by producing an audible signal, such as a tone or melody, upon detecting the transmitted RF signal.
One drawback of using a prior art wireless doorbell system is the aesthetic appearance of the transmitter. Because metal tends to act as a shield to RF transmissions, that is, it reduces the strength of the RF signals emanating from the transmitter, wireless doorbell transmitters are generally housed in plastic cases to allow the RF signals to radiate unimpeded from the transmitter the necessary distance to the receiver.
A further drawback of prior art doorbell transmitters housed in a plastic case is that the color or finish of the plastic oftentimes will not match the decorative trim at the entrance area of a residence. This trim might typically include polished brass doorknobs, kick plates or lighting fixtures.
Yet another drawback is that the plastic casing of prior art doorbell transmitters may crack and become unsightly after some period of exposure to the temperature extremes of the weather and the sun's ultraviolet rays. Additionally, the plastic color or finish of the prior art doorbell transmitters tends to fade over time creating a less than pleasing appearance.
Finally, another draw back of using a prior art plastic doorbell-transmitter is its lack of physical security because it is made of an easily vandalized plastic case.
Some prior art doorbell transmitters have used a limited amount of a thin metal coating on their top surface in an effort to improve the visual appearance of the doorbell transmitter without reducing the effective range of the RF transmissions to unacceptable levels. For example, the Dimango@ Model RC3321 uses metal paint or a similar metallic-based coating on but a small area (the top surface only) of the plastic case. While such a transmitter may have an acceptable effective range, it does not meet the aesthetic requirements of matching the styling and finish of nearby entranceway trim since it does not have the appearance of metal, nor does this prior art transmitter offer the longevity or physical security of a solid metal casing.
Heretofore a wireless doorbell transmitter having its RF source enclosed within a solid metal case would have such a limited effective range that its use would be unacceptable in a residential dwelling.